The 55-year-old has had a history of health problems in recent years. Earlier this season, Kubiak missed a game in San Diego due to a “complex migraine condition.” In 2013, he suffered a mini-stroke during a game while he was head coach of the Houston Texans.

Kubiak has a long coaching career in both college and professional football. He has won four Super Bowls, three with Denver and one with the San Francisco 49ers. His most recent championship came last year when the Broncos won Super Bowl 50.

As of Sunday morning, neither Kubiak, nor the Broncos organization had commented on the report.